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Mars Sample Return
JRehling
post Sep 4 2019, 03:49 AM
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QUOTE (John Whitehead @ Sep 3 2019, 10:30 AM) *
Regarding a heliocentric orbit close to that of Mars (roughly circular), the delta-V would be significantly greater than the elliptical orbit from Earth to Mars


This is what I had in mind from the gravity assist, not a chemical burn.

Looking at the gravity assists involved in Messenger, I see that the spacecraft and a given planet always met up after one or more times the planet's own orbital period. So, perhaps it would be feasible to encounter Mars for a gravity assist, then return to Mars after ~1.5 martian years, in a more favorable season. In the case of Messenger, a combination of gravity assists and chemical engine burns were utilized, but the chemical burns were of comparatively low delta-v.
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mcaplinger
post Sep 4 2019, 07:52 PM
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QUOTE (John Whitehead @ Sep 3 2019, 06:54 PM) *
Amazingly, the article almost completely ignores the need to create a MAV.

In all fairness, I believe this article was written in response to some ESA effort to develop a baseline for the Earth return spacecraft. I've never heard of an international mission where the MAV was provided by ESA.

That said, I agree with you that the MAV continues to get little attention. Maybe JPL is working on it and just not saying much about the effort.

There was a big conference about MSR in Berlin in 2018 (I'm sure discussed on this thread but I haven't checked) -- https://atpi.eventsair.com/QuickEventWebsit...ple-return/home -- which was entirely about how wonderful MSR was going to be without any real mention of the MAV at all.


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jccwrt
post Sep 4 2019, 08:25 PM
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Yeah, I wrote the article mostly to summarize the mission architecture as presented at 9th Mars and some of the community discussion with it. The description of the ascent vehicle took less than 30 seconds, so there wasn't a lot to write about. I'll be the first to say it's not a holistic view of the MSR program, since 9th Mars is primarily a geology conference and so most of the discussion centered on how it would impact science research. I'm not sure if the lack of engineering detail is a function of the audience or a lack of movement on the tech development side.
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John Whitehead
post Sep 5 2019, 07:33 PM
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QUOTE (mcaplinger @ Sep 4 2019, 07:52 PM) *
I agree with you that the MAV continues to get little attention. Maybe JPL is working on it and just not saying much about the effort.

JPL and MSFC have published a bunch of MAV papers in recent years, primarily at the IEEE Aerospace Conference and at the AIAA Propulsion and Energy Forum. See my posts in this UMSF topic, number 301 (August 2018) and number 351 (June 2019) for my perspective at those times. The MAV designs remain notional, while the engineering teams are mostly focused on propellants and combustion. Very little is said about the huge challenge of making the parts lightweight enough to fly. If the latter is happening, why would they not say so?

The latest two AIAA papers from August 2019 do not indicate a huge leap forward this year. One of them is titled, "A Design for a Two-Stage Solid MAV," but considering the content, a better title would have been, "Solid Rocket Motor Design Trades for a Notional Two-Stage MAV." Nothing new is said about the need to make solid propellant burn much slower than typical, and nothing new is said about including nozzle steering that is not terribly heavy (see my post 351). The paper about the hybrid propulsion MAV says they are still having fundamental problems including nozzle erosion and the need to add a new liquid fuel subsystem to keep the solid fuel burning correctly.

QUOTE (mcaplinger @ Sep 4 2019, 07:52 PM) *
There was a big conference about MSR in Berlin in 2018 (I'm sure discussed on this thread but I haven't checked) -- https://atpi.eventsair.com/QuickEventWebsit...ple-return/home -- which was entirely about how wonderful MSR was going to be without any real mention of the MAV at all.

The one detailed mention of the MAV at the Berlin conference was my own submission, as noted in my post number 301, and here is the link again.
https://www.hou.usra.edu/meetings/marssampl...18/pdf/6035.pdf

QUOTE (jccwrt @ Sep 4 2019, 08:25 PM) *
Yeah, I wrote the article mostly to summarize the mission architecture as presented at 9th Mars and some of the community discussion with it. The description of the ascent vehicle took less than 30 seconds. I'm not sure if the lack of engineering detail is a function of the audience or a lack of movement on the tech development side.

Justin, thank you for responding here. Did someone at 9th Mars actually say that the "rover" would launch the samples as you wrote? More importantly, why is there so little interest in talking about the little tiny rocket that can launch off a planet, the one aspect of the MSR mission that has the least previous experience to build upon? Shouldn't the Planetary Society be promoting this really cool engineering challenge, to help make it happen? I have explained the situation to Casey Dreier and Bruce Betts, but they are too busy to prioritize the MAV. Planetary Society outreach could be building upon the widespread fascination with rockets, e.g. SpaceX activities, and kids everywhere playing with little rockets.

Regarding your comment about the audience at 9th Mars, why should Mars scientists have no interest in the one most new and challenging thing that is needed to get their "data" back to the lab? My analogy is astronomers not being interested in projects to create new telescopes (no chance of such apathy).
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Phil Stooke
post Sep 5 2019, 08:21 PM
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For 'Mars scientists' read 'Mars geologists' (or other disciplines in the planetary sciences). The development of a MAV is an engineering challenge entirely outside their expertise. It's the rocket engineers who need to be involved, not Mars scientists. And I expect that is all happening below the radar.

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mcaplinger
post Sep 5 2019, 11:16 PM
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QUOTE (John Whitehead @ Sep 5 2019, 11:33 AM) *
why is there so little interest in talking about the little tiny rocket that can launch off a planet...

I daresay a combination of 1) people only being interested in their own little niches, combined with 2) a parade of technologists overselling their capabilities. Not many people seem aware of how immature the specifics of the MAV design are.

That said, I do remain convinced that this is a solvable problem, if the groups involved were given unambiguous direction and funding to solve it. Nothing clarifies a development activity like the opening of a launch window approaching on the calendar. Though I suspect if this ever happens there will be missteps and blind alleys along the way.


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jccwrt
post Sep 6 2019, 12:33 AM
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QUOTE (John Whitehead @ Sep 5 2019, 01:33 PM) *
Justin, thank you for responding here. Did someone at 9th Mars actually say that the "rover" would launch the samples as you wrote? More importantly, why is there so little interest in talking about the little tiny rocket that can launch off a planet, the one aspect of the MSR mission that has the least previous experience to build upon? Shouldn't the Planetary Society be promoting this really cool engineering challenge, to help make it happen? I have explained the situation to Casey Dreier and Bruce Betts, but they are too busy to prioritize the MAV. Planetary Society outreach could be building upon the widespread fascination with rockets, e.g. SpaceX activities, and kids everywhere playing with little rockets.

Regarding your comment about the audience at 9th Mars, why should Mars scientists have no interest in the one most new and challenging thing that is needed to get their "data" back to the lab? My analogy is astronomers not being interested in projects to create new telescopes (no chance of such apathy).


Sorry, the "rover" launching the MAV was a mistake on my part, it should have read "lander platform", on which the MAV is mounted. The configuration they showed a rendering of was something like a small rocket mounted on an Phoenix/Insight propulsive platform, with the rocket erector assembly replacing the instrument deck. I'm not sure if NASA/JPL has started using it publicly, since I didn't find the picture before the article went to press.

The engineering challenge is something the Planetary Society absolutely could promote, but for the purposes of the article I just wanted to report the new architecture details and the reception by the Mars planetary science community. There were only a handful of engineers present (mostly MER/MSL and ISRU folk) so most of the discussion centered around the practical impacts of MSR on mission planning and research for the next decade. Like Phil said, most of the engineering stuff is outside our expertise.

The apathy that does come through in the article, I think, comes from the having been burned with MSR a couple of times plus a bit of conservatism in sticking with what has worked. As an early (early) career Mars researcher myself, I am a little worried about MSR turning into an all-or-nothing approach.
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JRehling
post Sep 6 2019, 04:21 AM
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Not to oversimplify the matter, nor pretend to have expertise in rocketry, but in considering MAV, I had a bit of an epiphany that conditions on the surface of Mars are considerably closer to those of interplanetary space than to those on the surface of the Earth. Drag should be about 1% of that for a launch from the surface of the Earth (though the integrated total drag for the ascent will be more than 1% of that for a launch from Earth) and Mars' surface gravity is less than half of that of Earth's. The problem seems a bit less daunting if one thinks of it not as some new and utterly different launch condition but as a scenario that is between two known scenarios a deep space burn and a launch from the surface of the earth.

None of that solves any engineering problems, but it does suggest that competent engineers have some solid foundations to build upon whether they think of this as a deep space burn but harder or as a launch from Earth but easier.
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John Whitehead
post Sep 6 2019, 06:15 AM
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QUOTE (Phil Stooke @ Sep 5 2019, 09:21 PM) *
MAV is an engineering challenge entirely outside their expertise. It's the rocket engineers who need to be involved, not Mars scientists.
Phil

I don't buy the argument that geologists can't know enough to ask worthy questions. I'm not a geologist, but I know what a volcano is, what an earthquake is, and what a sedimentary rock is. Rocket propulsion is all about conservation of momentum, with a changing mass as propellant is expended. Did the geologists not take freshman physics? Rocket vehicle capability is limited by the energy in chemical bonds and the strength of metal, including weakening at elevated temperatures and the potential for cracks in thin tank walls, all of which seems to me like the kinds of things that geologists think about (just substitute "rock" for "metal"). Or do I have to say "geophysicist" to expect that these fundamentals would be understood?

QUOTE (Phil Stooke @ Sep 5 2019, 09:21 PM) *
And I expect that is all happening below the radar.
Phil

What is the basis for "expecting," or is it only "hoping"? Are we to believe that the years of publications about the gallant efforts to make the hybrid propulsion work, is just a cover story? And the honesty of the researchers in describing the difficulties is something other than that? And there is a hidden team of engineers who are not permitted to publish the real progress? Why would this happen, and why would the "better" engineers put up with this situation? I agree that we can all "wish" (versus "expect") there is MAV progress behind the scenes, but shouldn't we care enough to actually find out?

QUOTE (mcaplinger @ Sep 6 2019, 12:16 AM) *
I daresay a combination of 1) people only being interested in their own little niches, combined with 2) a parade of technologists overselling their capabilities. Not many people seem aware of how immature the specifics of the MAV design are.

Based on my past experience being funded by NASA to do research and development for a MAV, and having been connected with the community of people doing space propulsion research, and having participated in multiple MAV discussions at JPL and at JSC, I agree the more likely reality is that the rocket engineers are struggling for funding, so there is some overselling, and there is no hidden progress toward a MAV.

QUOTE (jccwrt @ Sep 6 2019, 01:33 AM) *
The engineering challenge is something the Planetary Society absolutely could promote

Great, so what's the next step to make this happen?

QUOTE (jccwrt @ Sep 6 2019, 01:33 AM) *
The apathy that does come through in the article, I think, comes from the having been burned with MSR a couple of times plus a bit of conservatism in sticking with what has worked. As an early (early) career Mars researcher myself, I am a little worried about MSR turning into an all-or-nothing approach.

If I understand these statements Justin, geologists worry that MSR is not going to happen. So why isn't this enough for them to get interested in learning about the MAV challenge?

QUOTE (JRehling @ Sep 6 2019, 05:21 AM) *
Not to oversimplify the matter, ... whether they think of this as a deep space burn but harder or as a launch from Earth but easier.

Yes, launching off of Mars is way harder than a deep space burn. Yes, the acceleration and velocity for Mars ascent are less than for launching from Earth. However, creating a MAV is not easier than launching from Earth because he MAV has to be small enough to deliver to Mars, along with its launch pad and related support equipment.
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jccwrt
post Sep 6 2019, 02:48 PM
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I think the fear on the geologists' part is that if it fails, we've lost a decade improving on the things we already know how to do and lose out on a decade of new data collection by orbiters and rovers. Mostly just trying to grapple with the risk of a very complex plan that NASA/ESA are still working out the details of.

As for your comment for the Planetary Society advocacy, I really don't know the next step. I'm just an occasional blog contributor, so I'm not involved with any of the advocacy programs.
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John Whitehead
post Sep 7 2019, 12:40 AM
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That's a key point, Justin. My perspective is that the best defense against big risks is to be better informed. The geologists (and the Planetary Society) should be demanding to know why so little has been said about the MAV, and what is a realistic mass budget for hardware versus propellant. Don't assume that NASA managers understand rocket engineering better than geologists can. A standard management protocol in big organizations is deliberate separation of decision-making from expertise.

Regarding the all-or-nothing approach, the hope in 1999 was to launch both a science rover and a MAV in 2003, and again in 2005. Multiple people including myself were trying to answer the question, "how small can a MAV be," so that MSR would not have to be one big risky expensive flagship mission. The MAV project manager in 1999 was a young software expert at JPL who proudly referred to himself as "the MAV MAN" (short for manager) working under the assumption that just getting a team together and organizing complexity would produce a MAV. People still don't seem to appreciate that there are two kinds of engineering difficulty, (1) complexity, and (2) physical limits. Big aerospace organizations are amazingly good at (1), but the MAV is (2).

On a fluke in 2004-2006 (a peer-reviewed technology NRA earmarked for low-cost Mars missions), NASA HQ funded my work toward miniature pump-fed liquid propulsion (like real launch vehicles scaled way down), then the money ran out. There could have been intentional research into making a smaller MAV, to avoid the all-or-nothing risk, but the system was stuck on the assumption that any MAV would be a "design-build" effort. Money allocated for cutting edge technology research always comes with the requirement to benefit multiple different missions, which leaves the MAV as an orphan problem, still unsolved.

In 2008, they invited me to a 3-day meeting in Houston, many engineers discussing all the different technology ingredients for a MSR mission. The NASA HQ person in charge was fresh off the space station project, which was all about being good at organizing huge complicated endeavors. Later at the airport we crossed paths, and she was terribly offended when I tried to explain to her that a MAV was not going to come from an orderly predictable bureaucratic process. Around 2010, hopes for making a small MAV were abandoned, which led to the flagship rover mission to leave sample containers lying on the ground (Mars 2020), and a separate big expensive mission for retrieval.

Before about 1995, some geologists did not want money spent on rover engineering, because that would be a big risk of time, money, and mission opportunities, versus continuing with Mars science as it was back then. Sound familiar? Should we wish that rovers had never been funded?

I offer the above summaries of events before your time, in hopes that knowing more of the history will help to reduce the chance of repeating past mistakes. The people working on MAV for the past few years don't seem to know (or care about) any of the history from before about 2010.
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mcaplinger
post Sep 7 2019, 04:26 PM
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QUOTE (John Whitehead @ Sep 6 2019, 04:40 PM) *
The geologists should be demanding to know why so little has been said about the MAV...

You're operating under the misperception that the science community is somehow "in charge" of mission architecture decisions. They aren't, except for some inputs at a very high planning level like the decadal survey, NAS, MEPAG, etc. I have already bemoaned the fact that IMHO there is a lot of unwarranted credulity displayed when technologists present to these bodies.

Even at the level of a single science instrument, science input is much more about capability than implementation.

There is every evidence that NASA HQ is making a good faith effort to accomplish MSR under significant budgetary and political constraints. In an ideal world, the MAV would be established and proven technology before such an effort was even planned. In reality, there doesn't seem to be enough money to do that development. So it will have to be done as part of the mission implementation itself, with concomitant cost and schedule risk.

I could go on, but I don't want to run afoul of rule 2.4 ("do not rant").


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John Whitehead
post Sep 8 2019, 12:23 AM
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Mike, I don't have the misperception you suggested, only saying that more people being more vocal might help. Considering your point that Mars scientists make "inputs at a very high planning level," the hope is for the MAV challenge to be appreciated at a "very high planning level," and for realistic MAV development to be part of the "good faith effort" that you refer to. I agree about the "unwarranted credulity."
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